Abstract
Ion temperature gradient (ITG) turbulence, also referred as ηi-mode, has been proposed as one of the dominant mechanisms determining the transport properties in the core of magnetic fusion devices such as tokamaks. In this work we intend to study the saturated ITG turbulence using a non-linear fluid description of the plasma including time evolution equations for perturbed ion density, parallel velocity and temperature in cylindrical-toroidal geometry. This problem has been treated numerically developing a parallel code to run in a Masivelly Parallel Machine with distributed memory, like CRAY-T3E. Finite differences in radius and Fourier mode expansion in poloidal and toroidal angles have been used. The numerical scheme is time implicit for linear terms and time explicit for nonlinear term. These nonlinear terms are quadratic nonlinearities that become convolutions of the Fourier components. The implicit linear term is solved with inversion of block tridiagonal matrices. To numerically advance these equations, a two-step, second-order accurate, time-centered advancement scheme is used. The serial code runs on all processors in a synchronous way, each processor works over a part of the problem. The distribution of calculations is: in harmonic Fourier to solve the implicit part (mainly invert matrices), and in radial points for the explicit calculations (mainly convolutions). In each time step, all processors must know the results obtained with the rest. To make this, the PVM (Parallel Virtual Machine) routines have been used to send and receive the data between processors.
Add the full text or supplementary notes for the publication here using Markdown formatting.
